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Review of Scientific Instruments / Volume 79 / Issue 9 / INVITED ARTICLE

Rev. Sci. Instrum. 79, 091301 (2008); doi:10.1063/1.2972112 (77 pages)

Invited Article: Deep Impact instrument calibration

Kenneth P. Klaasen1, Michael F. A’Hearn2, Michael Baca3, Alan Delamere4, Mark Desnoyer5, Tony Farnham2, Olivier Groussin2, Donald Hampton6, Sergei Ipatov2, Jianyang Li2, Carey Lisse7, Nickolaos Mastrodemos1, Stephanie McLaughlin2, Jessica Sunshine2, Peter Thomas5, and Dennis Wellnitz2

1Jet Propulsion Laboratory, California Institute of Technology, Mail Stop 306-392, 4800 Oak Grove Dr., Pasadena, California 91109, USA
2Department of Astronomy, University of Maryland, College Park, Maryland 20742-2421, USA
3Science Applications International Corporation, 5180 Parkstone Drive, Suite 100, Chantilly, Virginia 20151, USA
4Delamere Support Services, 525 Mapleton Ave., Boulder, Colorado 80304, USA
5Cornell University, Space Science Building, Ithaca, New York 14853, USA
6Ball Aerospace and Technologies, 1600 Commerce St., Boulder, Colorado 80301, USA
7Johns Hopkins University Applied Physics Laboratory, SD/SRE, MP3/W-155, 7707 Montpelier Road, Laurel, Maryland 20723, USA

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(Received 9 August 2007; accepted 18 July 2008; published online 25 September 2008)

Calibration of NASA’s Deep Impact spacecraft instruments allows reliable scientific interpretation of the images and spectra returned from comet Tempel 1. Calibrations of the four onboard remote sensing imaging instruments have been performed in the areas of geometric calibration, spatial resolution, spectral resolution, and radiometric response. Error sources such as noise (random, coherent, encoding, data compression), detector readout artifacts, scattered light, and radiation interactions have been quantified. The point spread functions (PSFs) of the medium resolution instrument and its twin impactor targeting sensor are near the theoretical minimum [ ∼ 1.7 pixels full width at half maximum (FWHM)]. However, the high resolution instrument camera was found to be out of focus with a PSF FWHM of ∼ 9 pixels. The charge coupled device (CCD) read noise is ∼ 1 DN. Electrical cross-talk between the CCD detector quadrants is correctable to <2 DN. The IR spectrometer response nonlinearity is correctable to ∼ 1%. Spectrometer read noise is ∼ 2 DN. The variation in zero-exposure signal level with time and spectrometer temperature is not fully characterized; currently corrections are good to ∼ 10 DN at best. Wavelength mapping onto the detector is known within 1 pixel; spectral lines have a FWHM of ∼ 2 pixels. About 1% of the IR detector pixels behave badly and remain uncalibrated. The spectrometer exhibits a faint ghost image from reflection off a beamsplitter. Instrument absolute radiometric calibration accuracies were determined generally to <10% using star imaging. Flat-field calibration reduces pixel-to-pixel response differences to ∼ 0.5% for the cameras and <2% for the spectrometer. A standard calibration image processing pipeline is used to produce archival image files for analysis by researchers.

© 2008 American Institute of Physics

Article Outline

  1. OVERVIEW
  2. INTRODUCTION TO THE MISSION
  3. INSTRUMENT DESCRIPTIONS
    1. CCD
    2. IR focal plane
    3. Inflight stimulators
    4. Quadrant nomenclature
    5. Image compression
    6. General flight performance
      1. HRI focus
      2. IR spectrometer operating temperature
  4. CALIBRATION DATA COLLECTION
  5. VIS CAMERA CALIBRATIONS
    1. Geometric calibrations
      1. Focal length and geometric distortion
      2. Relative boresight alignments
    2. Spatial resolution
      1. MRI and ITS point spread functions
      2. HRI point spread function
      3. HRI deconvolution
    3. Radiometric calibration
      1. Linearity
      2. Gain/full well
      3. Zero-exposure level
      4. Frame transfer smear
      5. Absolute sensitivity
      6. Individual pixel response
      7. Noise
      8. Scattered light
      9. Charge bleeding/residual
      10. Radiation noise
  6. IR SPECTROMETER CALIBRATIONS
    1. Geometric calibrations
      1. Focal length
      2. Relative boresight alignments
      3. Slit alignment
    2. Spatial resolution
    3. Radiometric calibration
      1. IR linearity
      2. Gain/full well
      3. Zero-exposure level
      4. Wavelength map
      5. Spectral resolution
      6. Absolute spectral sensitivity
      7. Individual pixel response
      8. Noise
      9. Scattered light
      10. Charge bleeding/residual
      11. Radiation noise
  7. PIPELINE PROCESSING
    1. Standard steps
    2. Calibration quality map
    3. Signal-to-noise ratio map
    4. Spectral registration maps
    5. Optional steps

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KEYWORDS and PACS

Keywords

aerospace instrumentation, calibration, CCD image sensors, comets, infrared spectrometers, planetary remote sensing, space vehicles

PACS

  • 95.55.Fw

    Space-based ultraviolet, optical, and infrared telescopes

  • 95.55.Qf

    Photometric, polarimetric, and spectroscopic instrumentation

  • 95.55.Pe

    Lunar, planetary, and deep-space probes

  • 96.30.Cw

    Comets

  • 07.57.Ty

    Infrared spectrometers, auxiliary equipment, and techniques

  • 07.57.Kp

    Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors

  • 06.20.fb

    Standards and calibration

ARTICLE DATA

Permalink
http://link.aip.org/link/doi/10.1063/1.2972112

PUBLICATION DATA

ISSN:

0034-6748 (print)  
1089-7623 (online)

Publisher:

$abstract.society.value is a Member of CrossRef American Institute of Physics

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